Evaluation of operative stress and peritoneal macrophage function in minimally invasive operations.

BACKGROUND: Laparoscopic operative procedures have decreased postoperative pain and the length of hospitalization. In addition, evidence supports a physiologic benefit from laparoscopic surgery. By analyzing several parameters of peritoneal macrophage function, we report a comparison of the magnitude of postoperative stress between two types of minimally invasive access techniques contrasted with an open laparotomy, in a murine model. STUDY DESIGN: Immature male A/J mice were exposed to pneumoperitoneum using carbon dioxide, gasless suspension, or laparotomy. Peritoneal macrophages were then harvested, and the number and viability of the macrophages from each group of mice were compared. Last, as a marker of postoperative stress, the in vitro production of nitric oxide and tumor necrosis factor alpha by these macrophages was determined. RESULTS: The number of peritoneal macrophages and the viability of the macrophages in the laparotomy group were significantly decreased 4 hours after operation compared with the minimally invasive and control groups. In addition, macrophage production of tumor necrosis factor alpha and nitric oxide, two markers of macrophage stress, 24 hours after operation was significantly increased in the laparotomy group compared with animals serving as controls. Gasless suspension and pneumoperitoneum decreased the number of macrophages to a lesser degree than did open laparotomy and did not affect macrophage viability. Moreover, gasless suspension and pneumoperitoneum did not lead to an increase in tumor necrosis factor alpha or nitric oxide production by peritoneal macrophages. CONCLUSIONS: Postoperative stress, assessed by a decrease in macrophage viability and an increase in cytotoxic cytokine production, is maximized after laparotomy compared with stress in murine hosts that underwent minimally invasive treatment. These data provide basic scientific evidence for the possible physiologic benefit of minimally invasive techniques.